JESK Journal of the Ergonomics Society of Korea

Effects of CCTV Viewing Angles on the Accuracy of Video-based Automated OWAS Assessment

Hangyeol Cho , Hyeonjong Yu , Kyung Min Kim , Won Guk Hwang , Young Woo Kim
10.5143/JESK.2026.45.4.297 Epub 2026 September 01

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Abstract

Objective: This study examined the effects of CCTV horizontal and vertical viewing angles and identified camera configurations that provide relatively stable performance in video-based automated OWAS assessment by comparison with motion capture data.

Background: Video-based human pose estimation has emerged as a promising alternative to conventional observational methods for musculoskeletal risk assessment. However, the influence of CCTV viewing angles on posture recognition accuracy has not been sufficiently validated.

Method: A laboratory experiment was conducted simulating a PE pipe manufacturing task. Video data were collected under five horizontal viewing angles (0~180°) and two vertical angles (30°, 60°). Video-based postures were estimated using MediaPipe, and motion capture data were used as ground truth. Performance was evaluated using joint angle errors and OWAS classification accuracy. A two-way repeatedmeasures ANOVA was applied to examine the effects of viewing angles.

Results: Viewing angle had significant effects on OWAS accuracy and joint-level estimation errors. Overall, the lower vertical angle (30°) yielded more stable performance than the higher vertical angle (60°). The highest OWAS code accuracy and the lowest OWAS action category RMSE were observed at the rear low-angle condition (180~30°), whereas side-oriented and high-angle conditions generally increased errors.

Conclusion: Among the tested conditions, low-angle front and rear views provided relatively stable performance for video-based automated OWAS assessment. The maximum exact OWAS code accuracy was 59.2%, supporting the use of single-view CCTV outputs for screening and comparative monitoring in conjunction with expert or sensor-based evaluation.

Application: The findings provide camera-placement guidance for automated posture monitoring; low-angle front or rear views are preferred whereas elevated or sideoriented installations can be supplemented with additional cameras or calibration procedures.

Keywords

Ovako Working posture Analysis System (OWAS) Viewing angle Musculoskeletal risk assessment Video-based posture analysis Assessment accuracy

References

1. Baldinger, M., Reimer, L.M. and Senner, V., Influence of the camera viewing angle on Openpose validity in motion analysis. Sensors, 25(3), 799, 2025.
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